Invasive Species Management

Need Noxious Weed Advice?

We are not able to provide site visits in 2021but are monitoring calls and questions. See our contact information on the right-hand side of this page.

Orange hawkweed flowerhead.What We Do

Orange hawkweed flowerhead.The Jefferson County Invasive Species Management program provides the public with information and offers solutions for managing invasive species and supports good stewardship of the land.  

We ensure the compliance with Colorado’s noxious weed, forest pest, and agricultural vertebrate pest regulations on private, county, and state lands.  We also provide technical assistance and support to county departments who are responsible for managing county owned lands.

The program coordinates with private, local, state, and federal agencies to achieve regional pest control.

Who We Are

Canada thistle flower.Our staff includes the Invasive Species Management Coordinator and limited summer help.

Bee of the Month - June 2021

Each month we will feature a bee profile.  There are 100’s of species of native bees in Jeffco.  Bees support many ecological processes but often go unnoticed.  


Parallel Leaf Cutter Bee

Megachile parallela

by Liam Cullinane, former Jeffco  ISM Specialist

Photo credit: bugguide

The parallel leaf cutter bee (Megachile parallela) is a solitary bee species in one of the largest bee genera. Bees in this genus have been known to exhibit a lot of variation in nesting habit, with some species nesting in natural cavities or hollowed out plant stems while others have been observed nesting in the ground. Regardless of nesting habit these bees, and this species, have a unique way of lining and closing their egg cells. They cut off pieces of leaf and line the entire egg cell to ensure the food supply of the egg does not desiccate while the egg is in hibernation. 

Another unique aspect of this bee species is that it collects pollen to bring back to its nest on the underside of its abdomen (see picture above). The long hairs under it’s abdomen facilitate efficient collection of pollen while it is foraging. This bee species is active from June to September and is a floral generalist.

Weed of the Month

Each month we will feature a noxious weed to help landowners identify weeds they may encounter on their property.

Eurasian watermilfoil

Photo credit: Elizabeth Brown

June 2021

Eurasian watermilfoil

Myriophyllum spicatum

This exotic species is an aquatic submerged plant that is one of the most destructive aquatic weeds known.  Eurasian watermilfoil (EWM) has leaves whorled around the stem with 14 or more leaflets on each side.  Fruiting stems with small yellow flowers form spikes above the water.  EWM is often confused with native milfoils.  Native species typically have fewer than 14 (5 to 10) leaflet pairs per leaf.  The exotic species can hybridize with the native milfoils.  Hybrids may require DNA testing to distinguish from non-hybrids.  

EWM aggressively forms dense mats that block the ability of sunlight to enter the water and stop the growth of native species, displaces wildlife habitat, and impede all forms of water-based recreation.  After fruiting, EWM makes fragments of the plant, these fragments are responsible for new colonies as they float to other areas, sink, and start new plants. Transport on boating equipment is a significant means of plant establishment in new bodies of water.  Any equipment used on or in the water can collect and spread this aquatic species.

This aggressive invader establishes in moving and standing waters and grows at a rate of approximately one foot per week.  It can infest an entire lake within a couple of years after introduction, EWM has less value as a food source for waterfowl than the native plants that it replaces. 

Remember to always clean, drain, and dry your boats, trailer, gear, and any equipment when playing or working in aquatic systems. It is not legal to transport watercraft over land with water drain plugs or aquatic vegetation on board per Colorado Parks and Wildlife (CPW) Aquatic Nuisance Species (ANS) regulations. 

According to CPW, this is the highest priority aquatic noxious weed in Colorado.  Millions of dollars are spent nationwide for control efforts.  If you detect EWM or any other ANS, please report it to The CPW ANS Program will verify the detection per regulation and will collaborate with CDA, the County, and other pertinent landowners or stakeholders to determine and implement the appropriate management response.


U.S. Geological Survey, Nonindigenous Aquatic Species Database

Minnesota DNR EWM

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A Landowner's Guide - Developing a Noxious Weed Management Plan

We developed this guide to assist landowners.  The information provides steps to develop a management plan for properties that have noxious weeds.

Download your copy

yellow_flag_iris Weed Spotter

The Weed Spotter program is a citizen science based effort to detect 6 high priority species on Jeffco Open Space parks.  Learn more at our Citizen Science page.

Myrtle spurge flower.Invasive Species 101 Webinar Series

A four session speaker series to inform landowners on invasive species terminology, identification, treatment, and the  latest trends.